Combustion chamber



June 12, 1956 5. J. MITCHELL COMBUSTION CHAMBER Filed April 16 1952 Inventor 0273' d; iii/77m? m M Attorneys United States Patent COMBUSTION CHAMBER Boris John Mitchell, Birmingham, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application April 16, 1952, Serial No. 282,509

3 Claims. (Cl. 123-191) This invention relates to engines for automotive and other uses and has particular relation to valve in head engines in which the major part of the combustion chamber employed is located in the piston of the engine.

It is proposed to provide a simple, inexpensive, easily manufactured engine capable of operating at high compression ratios and of improving the octane rating of fuels employed in operating the engine. To accomplish these ends, it is proposed to provide an engine head having a planar wall in which the valves and spark plugs may be located in directly opposed relation to the pistons of the engine. This Wall also is disposed normally with respect to the cylinders of the engine and forms one wall of the combustion chambers of the engine. Directly opposed to such wall it is proposed to provide in each piston of the engine a concave wall of substantially constant curvature, the center of which is outside of the combustion chamber, beyond the planar wall in the head and on the extended axis of each of the cylinders of the engine. The pistons of the engine therefore will be symmetrical in all sections through the axes of the cylinders of the engine. The spark plugs may be located in the planar wall as near the axes of the cylinders of the engine as is possible. The valves preferably should be located in the head in such manner that the valves do not extend outwardly beyond the limits of the cylinders. In the event the spark plugs cannot be located at a central part of the combustion chambers, then the spark plugs should be positioned at such angles in the head that the cavities in which the ends of the spark plugs terminate and the chambers in the end of the spark plugs surrounding the spark gap terminals thereof are directed toward the central parts of the combustion chambers of the engine. It is also proposed to reduce the quench areas by enlarging the chambers in the pistons until each chamber covers nearly all of the head end of the piston. The quench area or clearance space in each cylinder is annular in formation and is of substantially equal depth and width around the entire periphery of the cylinders so as to eliminate violent local turbulence which might otherwise be caused by the high velocity displacement of gas from between the piston and the head at the end of the compression stroke of the engine. With this quench area reduced to a minimum and being of equal extent throughout the entire periphery of each cylinder, there tends to be a balance affecting the pistons in the cylinders of the engine which minimizes engine roughness.

In the drawings:

Figure 1 is a transverse sectional view through an engine having a combustion chamber embracing the principles of the invention.

Figure 2 is a bottom plan view of the head, valves and spark plugs employed in the engine disclosed by Figure 1.

The engine disclosed by Figure 1 comprises an engine block 11 formed to provide a cylinder 12 for receiving a reciprocating piston 13 having a piston pin 14 by which the piston 13 is mounted for reciprocating move- 2,749,900 Patented June 12, 1956 "ice ment upon the end of the connecting rod 16. An engine head 17 is secured by bolts 18 upon an engine gasket 19 separating the head and block 17 and 11. The head 17 has a plane surface indicated at 21 extending normally to the axis of the cylinder 12 and directly opposed to the end of the cylinder 12. The head 17 has an exhaust valve 22 and an inlet valve 23 mounted in such a way that the lower surfaces of the valves form substantially a continuation of the plane surface 21. The valves 22 and 23 which are adapted to close exhaust and inlet passages formed in the head 17 are resiliently held in closed position by springs 24 and are mechanically opened by rocker arms 26. Rocker arms 26 are mounted on a rocker shaft 27 which is secured to a head 17 upon the rocker shaft supports indicated at 28. The rocker arms 26 are operated by push rods 29 which may be actuated in any suitable manner as by the camshaft of the engine 10. Cover 31 may be employed for covering the actuating mechanism for the valves 22 and 23. The valves 22 and 23 may be provided with annular clearance spaces indicated at 32 which are formed around the valves in the plane surface indicated at 21. The spark plug 33 is located as near to the axis of the cylinder 12 as is possible, although in the present instance the relation between the size of the valves 22 and 23 and the diameter of the cylinder 12 requires that the spark plug 33 be offset a short distance from the axis of the cylinder 12. In such event, it is desirable to mount the spark plug at an angle with respect to the axis of the cylinder 12 but in such position that the axis of the spark plug extended Will be directed toward the axis of the cylinder 12. The terminal end of the spark plug 33 therefore extends into a small recess 34 which is formed in the upper wall 21 and this recess and the annular cavity in the end of the spark plug 33 is directed toward the central part of the combustion chamber of the engine. The spark gap 36 between the terminals 37 of the spark plug 13 is therefore located in such position as to ignite the charge near the central part of the combustion chamber of the engine. A line-ofcenters through the valves 22 and 23, as seen in Fig. 2, is also offset from the axis of the cylinder 12 and is thus eccentrically disposed to the firing chamber. The end wall 38 of the piston 13 is formed in such a way as to provide a concave surface 39 of substantially uniform curvature which is formed in the end wall 38 from a center of curvature on the axis of the cylinder 12 and considerably beyond the plane surface indicated at 21. The space between the concave surface 39 and the plane surface 21 therefore provides a firing chamber 41 having the greatest depth at the axis of the cylinder 12 and decreasing in depth at the same rate in all directions toward the peripheral edge of the surface 39. Beyond the edge of the surface 39 is a minimum annular clearance space 42 of equal depth and equal width throughout the periphcry of the cylinder 12. It will be seen that the combustion chamber of the engine comprises the chamber 41, the clearance space 42, the clearance spaces 32 and the space at the end of the spark plug and within the pocket or cavity 34.

It will be apparent that the first part of the charge to be ignited at the spark gap 36 will tend to be directed toward the central part of the combustion chamber of the engine from which the charge will tend to burn at a substantially equal rate in all directions. Since the clearance or quench space 42 is of uniform width around the cylinder and is relatively narrow, there will be little of the total quality of the charge left to burn after the burning of the charge is completed in the chamber 41, the clearance spaces 32 and the pocket 34.

I claim:

1. An engine comprising a cylinder having an inner wall surface, a head and a piston with said piston being reciprocably mounted in said cylinder, said head having an inner wall formed to provide substantially a continuous and plane inner wall surface closing the end of said cylinder, said piston having an end wall formed to provide a concentrically disposed and shallow and spherical wall surface forming a depression in the end of said piston and a concentrically disposed annular wall surface surrounding said spherical wall surface and terminating at the inner wall surface of said cylinder, the inner wall surfaces of said piston, and said head and said cylinder being formed to provide a combustion chamber for said engine and including a firing chamber formed between said inner wall surface of said head and said spherical wall surface of said piston and communicating with the inner edge of a minimum mechanical clearance space formed between said inner wall surface of said head and said narrow annular wall surface of said piston, a spark plug secured in said head and having the spark gap terminals thereof extending through said head and adjacent one side of said firing chamber, a pair of inlet and exhaust valves disposed in said head and having a line-of-centers eccentrically disposed with respect to the firing chamber and opening inwardly through said inner wall surface of said head and extending across substantially the entire area between said spark plug and the inner wall surface of said cylinder remote from said spark plug and having the inner surfaces thereof extendingsubstantially in the plane of said inner wall surface of said head.

2. An engine as defined by claim 1 and in which the axis of said spark plug is obliquely disposed with respect to the axis of said cylinder and extends inwardly toward said axis within said cylinder and in which the spark gap terminals thereof are disposed in a shallow chamber formed in said inner wall of said head and in open communication with said firing chamber.

3. An engine as defined by claim 1 and in which shallow annular clearance spaces are formed in the inner wall of said head and around said valves and in open communication with said firing chamber.

References Cited in the file of this patent UNITED STATES PATENTS 2,184,357 Mallory Dec. 26, 1939 2,402,213 Starr June 18, 1946 FOREIGN PATENTS 177,409 Great Britain Mar. 30, 1922 356,366 Great Britain Sept. 10, 1931 415,976 Great Britain Sept. 6, 1934 

